In the case of a multiple layer recording material, it is preferable to prepare the material in such a manner that the adhesive strength between its layers can be controlled. Even in the case of a monolayer recording material, it may be convenient for many purposes if the material is prepared in such a manner that the adhesive strength between its supporting body and the monolayer can be controlled.
For example, a means for reducing the adhesive strength between layers making use of the effect of light has been disclosed in European Patent 0,156,535, in which a surfactant is formed when the layers are exposed to light. Also, a delamination development method has been disclosed in Photographic Science and Engineering, Vol. 22, No. 3, pp. 138-141 (1977), in which delamination is effected by the formation of gas from a diazo compound or an azide compound when the compound is exposed to light. Neither of them, however, seems to have satisfactory effect.
When a 2-diazo-1,2-quinone compound is exposed to light, it is converted into nitrogen gas and an indene carboxylic acid derivative induced by Wolff rearrangement. Recording materials prepared by making use of such an optical rearrangement reaction, especially positive type sensitive compositions, have been disclosed, for example, in U.S. Pat. No. 3,046,110, U.S. Pat. No. 3,046,111, U.S. Pat. No. 3,046,123, U.S. Pat. No. 3,046,124, U.S. Pat. No. 3,106,465, U.S. Pat. No. 3,130,047, and JP-B-46-21247 (corresponding to U.S. Pat. No. 3,640,992) (the term "JP-B" as used herein means an "examined Japanese patent publication"). However, there are no reports on the application of the optical rearrangement reaction to a process for the reduction of adhesive strength between layers with the aid of exposure to light.
Also, changes in the adhesive strength between a layer and a base board caused by the photolysis of these diazo compounds have been applied to dry type image formation processes. For example, an image forming process has been disclosed in JP-A-52-57819 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). According to this process, a transparent plastic film coated with a layer of a sensitive composition comprising a diazonium salt and a binder is superposed on a supporting sheet coated with an adhesive layer to prepare a laminate. When the thus prepared laminate is exposed to light and then the plastic film is delaminated from the supporting sheet, the unexposed portion of the sensitive composition layer remains on the transparent plastic sheet while the exposed portion remains on the supporting sheet.
In addition, processes for the formation of relief images have been disclosed, for example, in JP-A-54-79032, JP-A-54-79033 and JP-A-54-79034 (corresponding to U.S. Pat. Nos. 4,210,711, 4,334,006 and 4,396,700). According to these processes, an imagewise forming material comprising a sensitive composition is superposed on a supporting sheet which is noncohesive at ordinary temperatures, and the thus prepared laminate is subjected to imagewise exposure and then heated at a temperature higher than the softening point of the sensitive composition. Thereafter, the recording material is delaminated from the supporting sheet at a temperature which is lower than the heating temperature. In this way, the exposed image portion of the sensitive composition layer is selectively adhered to the supporting sheet to form a relief image.
However, because of an insufficient difference between the adhesive strength of the exposed and unexposed portions, none of these dry type processes can produce satisfactory images.
An image receiving sheet which comprises two image receiving layers of organic polymer materials superposed on a support has been disclosed in JP-A-61-189535 (corresponding to U.S. Pat. No. 4,766,053), in which the delamination strengths between the two image receiving layers and between the second image receiving layer and an image layer can be controlled in such a manner that the image layer can be transferred onto a permanent support not only singly but also together with the second image receiving layer at will. This image receiving sheet has an advantage in that optical gain of an image can be controlled by either introducing or not introducing a step for the transfer of the second image receiving layer and by changing the thickness of the second image receiving layer to be transferred. In addition, because of the thickness of the image receiving layer being thin on the image layer, the image receiving layer can reproduce the irregularity of the surface of the permanent support more accurately to give a natural matting effect. This image receiving sheet, therefore, can be used suitably for the preparation of a color proof having excellent print approximation.
This process, however, has the following problems with regard to the setting condition of the adhesiveness between the first and second image receiving layers.
1) The adhesiveness between the first and second image receiving layers should be strong when an image is transferred to the image receiving sheet (if the adhesiveness is too weak, delamination will occur between the first and second image receiving layers when the image support is delaminated).
2) The adhesiveness between the first and second image receiving layers should be weak when an image layer is transferred to a permanent support (if the adhesiveness is too strong, picking will occur when the image receiving sheet support is delaminated).